Hollow core door construction



Feb. 28, 1967 5, 51-550 3,395,992

HOLLOW CORE DOOR CONSTRUCTION Filed June 8, 1964 5 Sheets-Sheet 2INVENTOR.

flame 605%60/ Feb. 28, 1967 B. e. STEED HOLLOW CORE DOOR CONSTRUCTION 3Sheets-Sheet 3 Filed June 8, 1964 INVENTOR. zfi/azhe go zeeaz UnitedStates Patent Ofllice 33%,992 Patented Feb. 28, 1967 poration ofOklahoma Filed June 8, 1964, Ser. No. 373,306 6 Claims. (Cl. 52-314) Thepresent invention relates to doors, partitions and similar prefabricatedpanel constructions, and more particularly, but not by way oflimitation, relates to a method for manufacturing hollow core doorshaving decorativelyengraved faces, to the resulting article ofmanufacture, and to an apparatus for performing the method.

As is well-known, many doors presently in use today have an interiorframe covering on each side of sheets of plywood. This type of door iscommonly referred to as a hollow core door. These doors are relativelyinexpensive due to reduced cost of materials and reduced cost offabrication, but in general are available only with plain faces due tothe fact that the plywood sheets are so thin that no decorative grooveor interruptions in the planar surface can be made. The doors which aregenerally considered to be more attractive are fabricated from aplurality of panels which are held by an interlocking framework. Ingeneral this type of door has a face which appears to be engraved inthat it has surface irregularities which produce an attractive design.However, the paneled doors of conventional construction aresubstantially more expensive than hollow core doors.

In accordance with the present invention, a hollow core type door,partition or other construction panel, may be engraved with grooves to asubstantial depth so as to interrupt the otherwise planar face andproduce a more attractive appearance simultating the more expensivedoors fabricated from panels. The door constructed in accordance withthe present invention is comprised of a frame formed of strips generallyoutlining the engraved design in the face of the door, a sheet ofmaterial covering the frame to form the face of the door, and a grooveformed in the face of the door having a depth greater than the thicknessof the sheet in zones shadowed by the strips.

In accordance with the method of the present invention, a frame isformed of strips generally outlining the door and the design to beengraved, a sheet of material is bonded to the frame, and grooves areformed in the sheet and the backing strip of greater depth than thethickness of the sheet to produce the desired engraved design.

In accordance with an important aspect of the invention the grooves aremade of irregular cross-sectional configuration by passing separaterouter tools along parallel paths spaced one from the other such thatthe opposite sides of the grooves are milled by the different tools.This process permits the formation of a non-symmetrical groove whichmore nearly simulates the conventional panel type door construction andin general eliminates the undesirable appearance which would result frommerely routing a conventional symmetrical groove on the face of thedoor.

The invention also contemplates a novel apparatus for manufacturing anengraved door or other panel of the type described comprised of supportmeans for supporting a door, a mill holder having two spaced rotaryshafts disposed at right angles to a door supported by the supportmeans, a milling tool rotated by each shaft having a sweep, and meansfor guiding the mill holder along a predetermined closed path such thatthe shafts travel along parallel closed paths spaced apart a distanceless than the combined sweep of the tools.

Therefore, an important object of the present invention is to provide ahollow core door having a more decorative appearance.

A further object of the present invention is to provide a hollow coredoor having an appearance simulating a more expensive panel type door.

Another object of the present invention is to provide a doorconstruction of the type described which may be economicallymanufactured.

A further object of this invention is to provide a process formanufacturing a door of the type described.

Still another object of this invention is to provide a process forforming a decorative groove in the face of a door or the like which isnot symmetrical about a center line, yet which may easily be formed insubstantially any pattern, including right angles.

A still further object of the present invention is to provide a processfor manufacturing a hollow core door of the type described on aneconomical mass production basis.

A still further object of this invention is to provide an apparatus forengraving doors and panels with unsymmetrical grooves of the typedescribed by a single pass of a milling tool.

Many additional objects and advantages will be evident to those skilledin the art from the following detailed description and drawings,wherein:

FIGURE 1 is a view of the face of a door constructed in accordance withthe present invention;

FIGURE 2 is a sectional view taken substantially on lines 22 of FIGURE1;

FIGURE 3 is a view of the interior frame of the door of FIGURE 1 andserves to illustrate one step of the method of the present invention;

FIGURE 4 is a sectional view similar to FIGURE 2 which serves toillustrate another step of the method of the present invention;

FIGURES 5a and 5b, taken in conjunction, illustrate further steps of themethod of the present invention;

FIGURE 6 is a somewhat schematic view illustrating a portion of anapparatus constructed in accordance with the present invention forengraving doors and the like in accordance with the method of theinvention;

FIGURE 7 is a top view of a portion of the apparatus of FIGURE 6; and,

FIGURE 8 is a side view of a of FIGURE 6.

Referring now to the drawings, a door constructed in accordance with thepresent invention is indicated generally by the reference numeral 10.The door 10 is comprised of an interior frame indicated generally by thereference numeral 12 and illustrated in FIGURE 3. The frame 12 iscomprised of peripheral strip members 14, 16, 18 and 20 which areinterconnected by miter joints and form the outline and edges of thedoor 10. Vertically-disposed interior strips 22, 24, 26 and 28 extendbetween the top and bottom peripheral strips 16 and 20 and are securedthereto. Transversely-extendingstrips 30, 32, 34 and 36 are connectedbetween the strips 22 and 24. Similarly, transverse strips 38, 40, 42and 44 are connected between the vertical strips 26 and 28. The stripsforming the frame 12 will customarily be of a relatively inexpensivewood. The strips are preferably interconnected -by glue or other bondingagent, but may be interconnected by any suitable means such as, forexample, nails. The width of the strips, particularly the interiorstrips, is greater than the width of the grooves to be milled therein ashereafter described.

Sheets of relatively thin plywood 46 and 48 are bonded to the oppositesides of the frame 12 and are co-extensive with the frame to form theopposite faces of the doors.

portion of the apparatus As illustrated, the door 10 has four simulatedpanels 50, 52, 54 and 56 which are formed by continuous grooves 58, 60,62 and 64, respectively.

As can be seen by reference to FIGURE 3 and to the dotted lines ofFIGURE 1, the interior strips of the frame 12 generally outline therespective simulated panels and in particular shadow or back up thegrooves outlining the simulated panels. For example, the strips 22, 34,24 and 36 generally outline the panel 54 and shadow the groove 62. Thegrooves, for example, groove 62 as best seen in FIGURE 2, are of greaterdepth than the thickness of the plywood sheet 46 and are thereforepartially formed in the strips 22, 34, 24 and 36. An identical orsimilar engraved pattern may be provided on the back side of the door 10as illustrated by the grooves 66 and 68 in FIGURE 2.

It will be noted that the grooves are not symmetrical and have a deepchannel portion 70, a relatively steeply sloping irregular outer wall70a, an irregular inner wall 70b of less slope. This groove constructionclosely simulates the appearance of conventional doors constructed froma plurality of panels by tongue and groove techniques and alsoeliminates the undesirable appearance which .a symmetrical groove wouldhave of being placed there purely for decorative purposes. Although asillustrated, the grooves define rectangular panels, it is to beunderstood that panels of substantially any shape may be provided, inwhich case the strips of the frame 12 would be so oriented as to shadowand back up the grooves.

In accordance with the method of the present invention, the interiorframe 12 is first fabricated substantially as illustrated in FIGURE 3.Then the sheets of plywood 46 and 48 are bonded to the frame by asuitable glue or other bonding agent. The grooves are thin milled in theface of the hollow core panel in the areas backed by the strips of theinterior frames to form the desired engraved design. As previouslymentioned, the grooves are cut to a depth greater than the thickness ofthe plywood sheets. The deep channel portion 70 and outer wall 70a ofthe grooves are first formed by a router tool 71 having a configurationsubstantially as shown in FIGURE a. The router tool 71 has an axis ofrotation 72 disposed normal to the face of the door. The routing toolpreferably has a vertical cutting edge 74 of greater depth than thethickness of the plywood 46 so as to reduce the likelihood of producinga ragged edge along the plywood. Next a second router tool 76 having aconfiguration substantially as illustrated in FIGURE 5b is used to formthe interior wall 70b. The second router tool 76 has an axis of rotation78 that is moved along a path spaced from andparallel to the pathfollowed by the axis of rotation 72 of the first router tool 71 by adistance less than the combined sweep of the two tools. As used herein,the sweep of each tool shall be considered as the distance from the axisof rotation to the outermost cutting edge. Therefore, if distancebetween the paths of the axes of rotation of the two tools is less thanthe combined sweep of the two tools, a single groove will be milled ormore precisely, routed. As illustrated, it will be noted that the sweepof the second tool 76 is less than the distance from the axis ofrotation 78 of the second tool to any portion of the opposite outer wall70a cut by the first router tool 71 so that the bottom channel 70 andwall 70a will be cut only by the first router tool and the opposite orinner wall 70b will be cut by the router tool 76. In accordance with thebroader aspects of the invention, it is not necessarily essential thatthe router tools be limited to forming only one wall of the groove. Anycombination of the overlapping router tools may be employed to cutvarious portions of the groove and form unsymmetrical grooves. However,when square corners are to be turned as in the case of the continuousgrooves illustrated in FIGURE 1, it is important that the router toolcutting the inner surface not cut any portion of the outer surface. Ifthe inner tool does cut a portion of the outer wall of the groove, it.will be impossible to turn a sharp or right angle corner because of thedifferent radii of the outer edge out by the two tools as the tools passaround the corners as will hereafter be described in greater detail.

An apparatus for manufacturing a door in accordance with the presentinvention is illustrated in FIGURES 68 and indicated generally by thereference numeral 100. The apparatus is comprised of a dual shaft millholder 102 from which a pair of spaced, parallel drive shafts 104 and106 extend. The mill holder 102 includes a suitable drive mechanism (notillustrated) for rotating the shafts 104 and 106 at a relatively highspeed. Milling cutters commonly referred to as router blades 108 and 110are mounted on the shafts 104 and 106. The router blades 108 and 110 maycorrespond in shape to the tools 71 and 76 heretofore described inconnection with FIG- URES 5a and 5b.

The mill holder 102 is suspended from a guide rail 112 for movementalong a predetermined path corresponding to a groove to be cut in theface of a door 10. The guide rail 112 has a first guide channel 114which receives a first guide pin 116. The guide pin 116 is preciselylined with the axis of rotation of the first shaft 104. A head portion118 is provided on the guide pin 116 and is re ceived in an enlargedportion 114a of the channel 114 to support the mill holder 102. A secondguide channel 120 is formed in the top of the rail 112 and receives :asecond guide pin 122 which is precisely aligned with the axis ofrotation of the second shaft 106 The guide pin 122 is connected to themill holder 102 by a bracket 124 extending around the interior edge ofthe guide rail 112. The first and second guide channels 114 and 120extend in parallel relationship with the centers thereof spaced apart adistance corresponding to the desired spacing between the axes ofrotation of the router blades, such as for example, the distance xillustrated in FIGURE 5a and 517. As previously described, the distancex is less than the combined sweep of the two milling or router blades108 and 110.

The guide rail 112 may be continuous and in order to outline a panel ofthe door 10 must turn four right angles by means of mitered cornerssubstantially as illustrated in FIGURE 6. In FIGURE 6 the guide channels114 and 120 are illustrated in dotted and solid lines, respectively. Theguide pin 122 is illustrated at the corner of the turn and, asillustrated, is designed to trail the guide pin 116. As will be noted inFIGURE 7, the bracket 124 extends diagonally forward from the guide pin122 by an angle of at least 45 in order to clear the inside edge 112a ofthe rail 112. A handle 126 may extend forwardly from the bracket 124 tofacilitate manually moving the mill holder 102 along the rail 112 aswill hereafter be described. Or if desired, the mill holder 102 can bemoved along the rail by any suitable mechanism (not illustrated).Spherical rollers 128 are rotatably received in sockets (notillustrated) in the mill holder 102 and are positioned to engage androll on the underside of the guide rail 112 and properly orient therouter blades with respect to the guide channels.

Door 10 or other workpiece is supported and may be raised intoengagement with the router blades 108 and 110 by a suitable support 130.A guide plate 132 may extend along two edges of the door at right anglesto properly orient the door with respect to the guide rail 112. Theguide plate 132 may be associated with a horizontallydisposed stop plate134 against which the upper face of the door is raised for both properlypositioning the upper face and also for securely holding the doorbetween the plate 134 and the support as the groove is cut in the door.

In operation, the support 130 is lowered until the door panel in theform illustrated in FIGURE 4 will slide under the router blades 108 and110 into engagement with the guide plate 132. After two adjacent edgesof the door are butted against the guide plate 132, the door will beproperly oriented with the backing strips of the frame beneath the guidechannels of the guide rail 112. The mill holder 102 is then energized torotate the router blades 108 and 110 and the support 130 raised untilthe door engages the stop plate 134 which may extend around theperiphery of the door. The operator moves the mill holder 102 along therail in a direction such that the router blade 108 precedes the routerblade 110. By pressing downwardly and outwardly on the handle 126, thespherical rollers 128 may be biased upwardly against the under surfaceof the guide rail 112 to assure that the shafts 104 and 106 are orientednormal to the face of the door 10 and also to insure that the guide pins114 and 122 are firmly pressed against the outer edges of the guidechannels 114 and 120, respectively.

As the leading guide pin 116 approaches a right angle corner, the pin isjammed tightly into the outer edge of the corner and then kicked aroundthe corner. The trailing guide pin 122 continues to follow until itreaches the position illustrated in FIGURE 7 at which time care is takento maintain the pin in contact with the outer edges of the guide channel120. By reason of the fact that the guide channels 114 and 120 arealways in parallel relationship and uniformly spaced and the guide pins116 and 122 are precisely aligned with the axes of rotation .of therouter tools, the router blade 110 will follow the router blade 108 inthe same relative position illustrated in FIG- URES 5a-5b and FIGURE 6at all times. In this regard it will be noted that it is desirable whenturning a right angle that the radius or sweep of the blade cutting theouter wall of the groove, i.e., router blade 108, be of minimum radiusso as to reduce the curvature of the outer edge of the final groove cutin the door panel to a minimum. It is important that the other routerblade 110 out only the interior wall .of the groove. If the sweep of theblade 110 is great enough to cut a portion of the outer wall of thegroove, a portion of the groove at the corner will not be out due to thedifferent sweeps of the router blades and the groove will haveundesirable anomalies at the corners. Each of the continuous grooves 58,60, 62 and 64 can be cut separately, or four separate guide rails andmill holder units 102 may be provided on a single system for eitherindividual manual operation or simultaneous mechanical operation.

From the above detailed description of preferred embodiments of theinvention, it will be appreciated that an improved hollow core door,partition or similar panel construction has been described. The door hasthe economical advantages of a hollow core construction, yet can bedecoratively engraved to produce any desired design. In particular, thehollow door may simulate a paneled door of more costly construction. Amethod for fabricating doors or other panels on an economical, massproduction basis With a minimum use of expensive fabrication materialshas also been described. The method includes a means for forming adecorative groove having an unsymmetrical cross section of substantiallyany shape to be formed. In particular, the method permits the simulationof a paneled door construction by reason of providing a means forturning right angle corners. An apparatus or system for manufacturingdoors and for engraving panels in general with unsymmetrical grooveswith considerable precision on a mass production basis has also beendescribed.

Although preferred embodiments of the invention have been described indetail, it is to be understood that various changes, substitutions andalterations can be made in the parts and combinations thereof and in thesteps and sequences thereof without departing from the spirit and scopeof the invention as defined by the appended claims.

What is claimed is:

1. A hollow core panel having an engraved design on the face thereofformed by grooves comprising:

a frame formed of strips defining the periphery of the 6 panel andstrips within the periphery generally outlining the engraved design,

a sheet of material bonded to each of the strips and covering the frameto form the face of the panel, and

grooves cut in the face of the panel through the sheet of material intothe strips generally outlining the engraved design to form the engraveddesign, the sheet of material being bonded to the strips along bothedges of the sheet formed by the grooves.

2. A hollow core panel having an engraved design in the face thereof asdefined in claim 1 wherein:

the grooves have a non-symmetrical cross-sectional configuration.

3. A hollow core panel having a design on the face thereof formed bygrooves comprising:

a frame formed of interconnected strips generally outlining the design,the strips leaving openings in the frame and having a width greater thanthe width of the grooves,

a relatively thin sheet of material bonded to one side of the frame andcovering the openings through the frame, and

grooves of greater depth than the thickness of the sheet cut through thesheet and into the adjacent strips to produce the design, the sheet ofmaterial being bonded to the strips along both edges formed by thegrooves to produce a hollow space defined by the sheet of material andthe strips.

4. A hollow core door having a design on one face thereof formed bygrooves comprising:

a frame formed of strips outlining the door and the design, the portionsof the strips shadowing the grooves having widths greater than thewidths of the grooves, the frame having opposite, generally planarsides,

a sheet of material bonded to each side of the frame forming oppositefaces of the door, and

grooves cut through one of the sheets of material into the adjacentstrips to a greater depth than the thickness of the sheet to form thedesign, the sheet being bonded to the strips along both edges of thegrooves to form a hollow core defined by the strips and the sheet.

5. A hollow core door as defined in claim 4 wherein:

both faces of the door are provided with groove designs.

6. A hollow core door having a simulated panel formed in the facethereof by an endless groove comprising:

a frame formed of strips outlining the door and the simulated panel, thestrips outlining the simulated panel having a width greater than thewidth of the corresponding portion of the groove,

a sheet attached to and covering one side of the frame,

and

an endless groove of greater depth than the thickness of the sheetformed in the sheet and the strips outlining the panel, the portion ofthe sheet within the endless groove being bonded to the frame around theperiphery of the sheet formed by the groove.

References Cited by the Examiner UNITED STATES PATENTS 1,046,075 12/1912Kelley 144136 2,245,468 6/1941 Dussol 52--314 2,311,590 2/1943 Feder 52314 2,517,901 8/ 1950 Luckenbach 144-144 2,524,593 10/1950 Deacy 523162,556,884 6/1951 Muller 161123 X 2,751,946 6/ 1956 Gramelspacher 144-3163,083,745 4/1963 MacDonald 144-316 REINALDO P. MACHADO, PrimaryExaminer.

HARRISON R. MOSELEY, Examiner.

K. DOWNEY, Assistant Examiner.

1. A HOLLOW CORE PANEL HAVING AN ENGRAVED DESIGN ON THE FACE THEREOFFORMED BY GROOVES COMPRISING: A FRAME FORMED OF STRIPS DEFINING THEPERIPHERY OF THE PANEL AND STRIPS WITHIN THE PERIPHERY GENERALLYOUTLINING THE ENGRAVED DESIGN, A SHEET OF MATERIAL BONDED TO EACH OF THESTRIPS AND COVERING THE FRAME TO FORM THE FACE OF THE PANEL, AND GROOVESCUT IN THE FACE OF THE PANEL THROUGH THE SHEET OF MATERIAL INTO THESTRIPS GENERALLY OUTLINING THE ENGRAVED DESIGN TO FORM THE ENGRAVEDDESIGN, THE SHEET OF MATERIAL BEING BONDED TO THE STRIPS ALONG BOTHEDGES OF THE SHEET FORMED BY THE GROOVES.